Real-time monitoring of physiological parameters in the study of Escherichia coli early response to peroxide stress

The response of aerobically growing Escherichia coli cultures to peroxide stress was studied using synchronous real-time monitoring of parameters pO2 (oxygen partial pressure), pH, Eh (redox potential of the culture), extracellular levels of K+ and S2-, in combination with traditional physiological, biochemical and genetic methods. A sharp increase in pO2 level in the medium caused by the destruction of H2O2 by endogenous catalases was observed in the early response to peroxide stress. The addition of 100 μM H2O2 provoked a reversible decrease in the specific growth rate, accompanied by an increase of extra- and intracellular glutathione and a short-term increase in sulfide production. Treatment with a high dose of H2O2 (10 mM) led to growth inhibition and a CFU loss, most pronounced in glutathione synthesis mutants. Simultaneously, in 8% of cells, the membrane potential decreased, a part of potassium was released into the medium, and the expression of the sulA gene, which is part of the SOS-regulon, increased. Application of an integrated approach to the study of stress revealed a close relationship between growth parameters (specific growth rate and survival), respiratory activity, sulfide production, and the ability of E. coli cells to maintain the membrane potential and K+ gradient.